The CARMENES search for exoplanets around M dwarfs. Detection of a mini-Neptune around LSPM J2116+0234 and refinement of orbital parameters of a super-Earth around GJ 686 (BD+18 3421)
Schmitt, J. H. M. M.; Amado, P. J.; Bauer, F. F.; Caballero, J. A.; Reiners, A.; Ribas, I.; Quirrenbach, A.; Béjar, V. J. S.; Guenther, E. W.; Henning, T.; Kaminski, A.; Kürster, M.; Montes, D.; Morales, J. C.; Tal-Or, L.; Zechmeister, M.; Passegger, V. M.; Cortés-Contreras, M.; Dreizler, S.; Jeffers, S. V.; Lafarga, M.; Rodríguez, E.; Lalitha, S.; Hagen, H. -J.; Galadí-Enríquez, D.; Oshagh, M.; Rodríguez-López, C.; Lodieu, N.; Herrero, E.; Perger, M.; Rosich, A.; González-Cuesta, L.; López-González, M. J.; Husser, T. -O.; Baroch, D.; Cardona Guillén, C.; Colomé, J.
Germany, Spain, Israel
Abstract
Although M dwarfs are known for high levels of stellar activity, they are ideal targets for the search of low-mass exoplanets with the radial velocity (RV) method. We report the discovery of a planetary-mass companion around LSPM J2116+0234 (M3.0 V) and confirm the existence of a planet orbiting GJ 686 (BD+18 3421; M1.0 V). The discovery of the planet around LSPM J2116+0234 is based on CARMENES RV observations in the visual and near-infrared channels. We confirm the planet orbiting around GJ 686 by analyzing the RV data spanning over two decades of observationsfrom CARMENES VIS, HARPS-N, HARPS, and HIRES. We find planetary signals at 14.44 and 15.53 d in the RV data for LSPM J2116+0234 and GJ 686, respectively. Additionally, the RV, photometric time series, and various spectroscopic indicators show hints of variations of 42 d for LSPM J2116+0234 and 37 d for GJ 686, which we attribute to the stellar rotation periods. The orbital parameters of the planets are modeled with Keplerian fits together with correlated noise from the stellar activity. A mini-Neptune with a minimum mass of 11.8 M⊕ orbits LSPM J2116+0234 producing a RV semi-amplitude of 6.19 m s-1, while a super-Earth of mass 6.6 M⊕ orbits GJ 686 and produces a RV semi-amplitude of 3.0 m s-1. Both LSPM J2116+0234 and GJ 686 have planetary companions populating the regime of exoplanets with masses lower than 15 M⊕ and orbital periods <20 d.
Table A.1 and A.2 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/627/A116